How static variable in classes being allocated in memory?

Question

class car
{
public:
    static int i;
};

int car::i = 7;
int main ()
{   
    cout << car::i;
    return 0;    
}

Is a static variable allocating memory because of it's definition outside class and declaring it inside class just to become a member of class? and why when it becomes constant we didn't define it outside class?

I understand that static variable being allocated in global and static variable segment in memory and static variable don't belong to any object.

Answer 1

How static variable in classes being allocated in memory?

Static class variables have static storage.